The invention relates to a method of setting the persistence of a mobile station in a cellular mobile radio network. The access probability of the mobile station can be considered for example as an instance of persistence.
In cellular mobile radio networks the available physical radio channels are divided up between the mobile radio subscribers in such manner that a subscriber is assigned a radio channel only for the duration of a communication connection. Here the assignment of the radio channels is controlled by the mobile radio network.
If the mobile station makes a transmission request, this request must start an access attempt on a radio channel specially intended for this purpose (random access channel) in contention with the other mobile stations in the same radio cell. If this access is successful, the mobile station is allocated a specified radio channel. If a collision occurs or if the transmission is disturbed by transmission errors, no such allocation takes place and the mobile station repeats the transmission.
Access procedures of this type are well known, being based on so-called S-ALOHA-protocols, and are used in various cable networks and radio networks.
The S-ALOHA-protocols are known for their stability problems in the case of a high offered traffic load. If the offered traffic exceeds a critical value, a simultaneous increase occurs in the number of collisions, the number of mobile stations with transmission requests increasing further as a result of the repetitions. To eliminate this overload situation, the persistence of the access of the mobile station is generally adapted to the current load. Here in general the access probability, the waiting time between two accesses, and the maximum number of access attempts are varied.
For differentiation between different priorities, the control of the persistence can additionally be used to give precedence to specific stations actually during access.
In accordance with the invention there is provided a method of setting the persistence of a mobile station (M) in a cellular mobile radio network, characterised in that the persistence is set in two steps, and specifically by a persistence rule (P) for the long-term adaptation and by load characteristic variables (p(i)) for the short-term adaptation.
The Invention provides a method of the type referred to in the introduction with which the persistence of the mobile station can be set with less delay, greater accuracy, greater stability and in a simpler manner.
The method according to the invention for setting the persistence of a mobile station in a cellular mobile radio network is characterised in that the persistence is set in two steps, and specifically by a persistence rule for the long-term adaptation and by load characteristic variables for the short-term adaptation.
In a development of the invention, a long-term persistence behaviour is calculated in the base station and transmitted in the form of the persistence rule to the mobile station. It is also possible to calculate a short-term persistence behaviour in the base station and to transmit this in the form of current load characteristic variables to the mobile station.
In another development of the invention, the persistence of the mobile station can be a function of the load characteristic variable of the priority in question and the sum of load characteristic variables of lower priorities.